Abstract
Brassica rapa NGATHA1 (BrNGA1) encodes a B3-type transcription factor. By analyzing Arabidopsis overexpressors of BrNGA1 (BrNGA1ox), we have previously demonstrated that BrNGA1 may be involved in negative regulation of cell proliferation during lateral organ and root growth. In the present study, we have found that BrNGA1ox seedlings grown in the dark display de-etiolation phenotypes, such as short hypocotyls, open and elongated cotyledons, and developing true leaves. BrNGA1ox seedlings as well as adult plants and calli are also resistant specifically to exogenous cytokinins. These data raise the possibility that the de-etiolation phenotypes of BrNGA1ox seedlings may result from an alteration in cytokinin response. We set out to test whether the de-etiolation phenotype is due to cytokinin overproduction or constitutively activated cytokinin response. First, BrNGA1ox was crossed to the CKX2ox plant, an overexpression line of CYTOKIN OXIDASE 2, which is responsible for degradation of active cytokinins. We found, however, no difference in the de-etiolation and shoot growth phenotypes between BrNGA1ox and BrNGA1ox CKX2ox plants. Next, we measured the transcripts level of ARR5 and ARR7, frequently employed as molecular markers for cytokinin signaling and yet found no difference in their transcripts levels of the wild-type and BrNGA1ox seedlings and shoots. These data indicate that biological role of BrNGA1 involved in de-etiolation seems to be associated with neither cytokinin overproduction nor its altered signaling. Possible molecular mechanisms by which BrNGA1 may interfere with cytokinin responses and etiolation are discussed.
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Argyros RD, Mathews DE, Chiang YH, Palmer CM, Thibault DM, Etheridge N, Argyros DA, Mason MG, Kieber JJ, Schaller GE (2008) Type B response regulators of Arabidopsis play key roles in cytokinin signaling and plant development. Plant Cell 20:2102–2116
Catterou M, Dubois F, Smets R, Vaniet S, Kichey T, Van Onckelen H, Sangwan-Norreel BS, Sangwan RS (2002) hoc: an Arabidopsis mutant overproducing cytokinins and expressiong high in vitro organogenic capacity. Plant J 30:273–287
Chaudhury AM, Letham S, Craig S, Dennis ES (1993) amp1- a mutant with high cytokinin levels and altered embryonic pattern, faster vegetative growth, constitutive photomorphogenesis and precocious flowering. Plant J 4:907–916
Chin-Atkins AM, Craig S, Hocart CH, Dennis ES, Chaudhury AM (1996) Increased endogenous cytokinin in the Arabidopsis amp1 mutant corresponds with de-etiolation responses. Planta 198:549–556
Chory J, Reinicke D, Sim S, Washburn T, Brenner M (1994) A role for cytokinins in de-etiolation in Arabidopsis. Plant Physiol 104:339–347
Gattolin S, Alandete-Saez M, Elliott K, Gonzalez-Carranza Z, Naomab E, Powell C, Roerts JA (2006) Spatial and temporal expression of the response regulators ARR22 and ARR24 in Arabidopsis thaliana. J Exp Bot 57:4225–4233
Hewelt A, Prinsen E, Schell J, Van Onckelen H, Schumülling T (1994) Promoter tagging with a promoterless ipt gene leads to cytokinin-induced phenotypic variability in transgenic tobacco plants: implications of gene dosage effects. Plant J 6:879–891
Higuchi M, Pischke MS, Mahonen AP, Miyawaki K, Hashimoto Y, Seki M, Kobayashi M, Shinozaki K, Kato T, Tabata S, Helariutta Y, Sussman MR, Kakimoto T (2004) In planta functions of the Arabidopsis cytokinin receptor family. Proc Natl Acad Sci USA 101:8821–8826
Kiba T, Aoki K, Sakakibara H, Mizuno T (2004) Arabidopsis response regulator, ARR22, ectopic expression of which results in phenotypes similar to the wol cytokinin receptor mutant. Plant Cell Physiol 45:1063–1077
Kiba T, Naitou T, Koizumi N, Yamashino T, Sakakibara H, Mizuno T (2005) Combinatorial microarray analysis revealing Arabidopsis genes implicated in cytokinin responses through the His>Asp phosphorelay circuitry. Plant Cell Physiol 46:339–355
Kieber JJ, Schaller GE (2010) The perception of cytokinin: a story 50 years in the making. Plant Physiol 154:487–492
Kuderová A, Urbánková I, Válová M, Malbeck J, Brzobogaty B, Némethová D, Hehátko J (2008) Effects of conditional IPT-dependent cytokinin overproduction on root architecture of Arabidopsis seedlings. Plant Cell Physiol 49:570–582
Kwon SH, Lee BH, Kim EY, Seo YS, Lee SM, Kim WT, Song JT, Kim JH (2009) Overexpression of a Brassica rapa NGATHA gene in Arabidopsis thaliana negatively affects cell proliferation during lateral organ and root growth. Plant Cell Physiol 50:2162–2173
Laxmi A, Paul LK, Raychaudhuri A, Peters JL, Khurana JP (2006) Arabidopsis cytokinin-resistant mutant, cnr1, displays altered auxin responses and sugar sensitivity. Plant Mol Biol 62:409–425
Li J, Nagpal P, Vitart V, McMorris TC, Chory J (1996) A role for brassinosteroids in light-dependent development of Arabidopsis. Science 272:398–401
Livak KJ, Schmittgen TD (2001) Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) method. Methods 25:402–408
Medford JI, Horgan RH, El-Sawi Z, Klee HJ (1989) Alterations of endogenous cytokinins in transgenic plants using a chimeric isopentenyl transferase gene. Plant Cell 1:403–413
Rashotte AM, Mason MG, Hutchison CE, Ferreira FJ, Schaller GE, Kieber JJ (2006) A subset of Arabidopsis AP2 transcription factors mediates cytokinin responses in concert with a two-component pathway. Proc Natl Acad Sci 103:11081–11085
Riefler M, Novak O, Strnad M, Schmülling T (2006) Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism. Plant Cell 18:40–54
Sakakibara H (2006) Cytokinins: activity, biosynthesis, and translocation. Ann Rev Plant Biol 57:431–449
Smigocki AC (1991) Cytokinin content and tissue distribution in plants transformed by a reconstructed isopentenyl transferases gene. Plant Mol Biol 16:105–115
Sun J, Niu QW, Tarkowski P, Zheng B, Tarkowska D, Sandberg G, Chua NH, Zuo J (2003) The Arabidopsis AtIPT8/PGA22 gene encodes an Isopentenyl transferases that is involved in de novo cytokinin biosynthesis. Plant Physiol 131:167–176
To JPC, Kieber JJ (2007) Cytokinin signaling: two-components and more. Trends Plant Sci 13:85–92
Tian Q, Reed JW (1999) Control of auxin-regulated root development by the Arabidopsis thaliana SHY2/IAA3 gene. Development 126:711–721
Vogel JP, Schuerman P, Woeste K, Brandstatter I, Kiever JJ (1998) Isolation and characterization of Arabidopsis mutants defective in the induction of ethylene biosynthesis by cytokinin. Genetics 149:417–427
Werner T, Motyka V, Laucou V, Smets R, Van Onckelen H, Schumülling T (2003) Cytokinin-deficient transgenic Arabidopsis plants show multiple developmental alterations indicating opposite functions of cytokinins in the regulation of shoot and root meristem activity. Plant Cell 15:2532–2550
Acknowledgments
This research was supported by the Korea Science and Engineering Foundation (R01-2008-000-20648-0); Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2009-00765517). We thank Dr. Thomas Schmülling for sharing CKX2ox lines and Doo Young Hwang for his excellent technical assistance.
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Kwon, S.H., Chang, S.C., Ko, JH. et al. Overexpression of Brassica rapa NGATHA1 Gene Confers De-Etiolation Phenotype and Cytokinin Resistance on Arabidopsis thaliana . J. Plant Biol. 54, 119–125 (2011). https://doi.org/10.1007/s12374-011-9150-2
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DOI: https://doi.org/10.1007/s12374-011-9150-2